It is a wonder of engineering, a beautiful testimony to the blend of function and aesthetics and a fitting addition to the bridges from the 19th and 20th centuries. I write, of course about the Queensferry Crossing, that marvellous tribute to worldwide ­co-operation by private commerce and ­government planning.

Like so many capital investment projects of such a grand scale it was typically expensive, at £1.3 billion, and while some argued that a tunnel could have been provided at a cheaper cost to the taxpayer and others believed it was not necessary at all, it did actually come in under its final budget. That’s a notable achievement in itself.

Still, I do have a gripe about the new bridge and was interested to see it raised last week by Tory MSP Jamie Greene, after he conducted some Freedom of Information enquiries. Sadly the bridge is not living up to its designed intentions, but this is not because of design flaws, but due to political correctness.

The new bridge has replaced the old bridge, but was limited by politicians to offer only two lanes each way. Surely it would have made sense to accommodate three lanes rather than two?

Such is the capacity that it has to carry – far, far in excess of when the first road bridge opened in 1964 – that cars are unlikely to find they can travel at the permitted speed of 70mph. This is disappointing, for the bridge was designed with an aerodynamic efficiency that shields cars from strong winds and allows them to travel faster than the speeds of the past (often limited to 30mph).

A Freedom of Information response has shown the average speed on the bridge at rush hour in the morning and evening is less than 25mph – far less than the 70mph speed limit – with an average speed of 24mph during the morning rush hour, and 21mph during the evening rush hour.

It’s not so much that a fast speed is important for its own sake, but a faster speed through the approach roads and over the bridge itself eases congestion and is of greater environmental benefit. Easing congestion was one of the stated aims and that is just not being met.

There is a way around this of course, but again political correctness has got in the way. When the need for the Queensferry Crossing was first debated it was thought it would replace the current Forth Road Bridge altogether, then, as it became apparent the Forth Road Bridge was not as badly corroded as had first been believed it was recognised that both bridges could be in operation. Unfortunately, politicians in government and at Holyrood took the ridiculous decision to limit the older bridge to only public transport – buses and taxis – missing the opportunity to double the capacity of all bridge ­traffic overnight. Congestion could have been significantly reduced and average speeds would be faster – as they were designed to be.

This could have been achieved by organising the feeder roads in such a way that traffic in both directions used the bridges, or one bridge was used for travelling north and another south. With some invention it could even have been possible to use three double carriageways for the busiest route (south in the morning and north in the evening) just like many rush-hour carriageways and bridges are altered in the US and Canada.

As Jamie Greene pointed out: “The disappointing reality is that most motorists using the Queensferry Crossing could be overtaken by a bicycle.”

One day I believe that, after spending all that money, common sense will prevail and both bridges will be open to all traffic. Until then, the Queensferry Crossing will remain a bridge too slow.